CLEVELAND, Ohio -- USC coach Clay Helton has led his team against some of the top quarterbacks in this draft, including UCLA's Josh Rosen. But he believes his own Sam Darnold is No.1.

"At the end of the day, he produces wins and I think he may have the highest ceiling of anybody in the draft because I still think there's so much growth for him and potential for him to get even better than he is right now,'' Helton told cleveland.com on Wednesday. "He's so great now, but he hasn't even touched the ceiling of where he's going to go to.''

Helton's opinion is consistent with that of NFL Network's Daniel Jeremiah, who has Darnold -- a strong candidate for the Browns at No. 1 -- as his top QB in this draft.

"I gave him the same grade that I gave Carson Wentz, so he would be tied at the top for me (since 2015),'' Jeremiah told the Browns in-house radio show Cleveland Browns Daily. "He's as good as any of the quarterbacks in the last three drafts."

Helton, who recruited Darnold out of San Clemente High when he was USC's offensive coordinator and quarterbacks coach, believes Darnold's accuracy is his strength. He completed 64.9 percent of his attempts in college, including 67.2 percent as a sophomore and 63.1 percent last season.

"His best attribute is to keep the play alive and create and keep his eyes downfield,'' said Helton. "Go back and watch his accuracy when he's on the move. It's as good as I've ever been around. His best accuracy is when things break down and he has to move, and that's the real world in elite college football as well as the NFL.''

Darnold's elusiveness on film is one of the things that stands out, and scouts note that his feet are better than Rosen's. The Browns are considering both QBs for one of their high first-round picks, along with Wyoming's Josh Allen and Oklahoma's Baker Mayfield. Louisville's Lamar Jackson is also on the radar.

"Sam is a 4.8 kid but he has exceptional change of direction,'' said Helton. "When you look at his change of direction, especially his pocket presence and his ability to keep his eyes downfield, he can sense peripheral pressure and step up or break contain.

"He also has those different arm angles. He doesn't have to step into his throw which I think is really big. He's just a ballplayer. He's got 'it.' He's like that great point guard that finds a way to get it done.''

Helton believes that turnovers won't plague Darnold, 20, in the NFL as they did in college. At USC, he threw 22 interceptions in two seasons, and lost 14 of his 21 fumbles in 27 starts. In 2017, he threw 13 interceptions against 26 TDs and lost nine fumbles.

"He has a 2:1 ratio right now touchdown to interception, and in his second year, those numbers were more like 4:1,'' he said. "A lot of that had to do for us with the personnel that was around him. We had a very young football team especially on the offensive line, when we got three injuries to our offensive line and some freshman had to play. Against Texas, the ball bounced off the facemask of a wide receiver and falls into the hands of a safety (for a pick-six). You need to look at each situation and look at the men around him.''

He added "at the end of the day, the greatest stat that matters is that he went 20-4 for us, won a Rose Bowl and a Pac-12 championship -- and that was all because of Sam Darnold.''

He acknowledged that USC's 24-7 loss to Ohio State in the Cotton Bowl wasn't the way Darnold wanted to end his career. He threw a pick-six and lost two fumbles.

"But that loss was on the whole team, not just Sam Darnold,'' said Helton.

Helton says Darnold's work in a stunning 52-49 victory over Penn State in the previous year's Rose Bowl, with 453 passing yards in a come-from-behind victory, is a more accurate example.

"He performs the best when the lights are the brightest and the pressure is on,'' Helton said. "To be that age and have two minutes on the clock with no timeouts having to go 80 yards and you do it to perfection; just to have that poise in that type of situation is who he is."

He has no doubt about Darnold's ability to lead a locker room. He told the story of freshman Darnold asking then-senior receiver JuJu Smith-Schuster to tone down a celebration after a catch in practice.

"He was only here five semesters for us, which is hard to believe," he said. "But he played at an extremely young age at a high level of maturity. That's one of his greatest attributes is his leadership ability and confidence in those situations.''

He said if the Browns draft Darnold, they will have solved their quarterback problems.

"They're getting a consistent force on a day-to-day basis that's going to bring what you need at the quarterback position,'' he said. "It starts with the intangibles, and his leadership and his work ethic on a day-to-day basis was infectious for us here and I know will carry over to whatever organization he goes to. He'll lift up that organization.''

Helton said Darnold won't have a difficult transition to a pro style offense because he played in one in college.

"Whether it's five-man multi-progression pass routes, whether it's diagnosing front and coverage as far as re-Miking and protection, whether it's having a full-field read, having to split the field in half ... he's had to be able to be able to learn at the pro level and make decisions.''

He said Darnold's processing speed will impress the Browns' staff when they put him on the board, which will happen during a private workout and subsequent visit to Cleveland.

"We had a coach on the field in Sam Darnold that we're truly going to miss,'' he said. "He was one of those guys that you could hand him the keys to the car and he could drive it. You know whoever gets him is going to be very, very happy with how he's been trained.''